1. Field of the Invention
The present invention relates to a flat image display apparatus utilizing an electron beam, such as a field emission display (FED). More particularly, the present invention relates to a light-emitting screen structure which emits light upon irradiation of an electron beam to display an image, and an image display apparatus using the light-emitting screen structure.
2. Description of the Related Art
Hitherto, electron-emitting devices have been utilized in an image display apparatus. For example, there is known a display panel in which an electron source substrate having a large number of electron-emitting devices formed thereon is arranged to face an opposite substrate including phosphors and a metal back for accelerating electrons emitted from the electron-emitting devices. The interior of the display panel is evacuated to a vacuum state. Such a flat electron-beam display panel is advantageous in reducing weight and increasing a screen size as compared with CRT (cathode ray tube) display apparatuses which have been widely used so far. Further, the flat electron-beam display panel can provide an image with higher brightness and higher quality than other flat display panels, such as a flat display panel using a liquid crystal, a plasma display, and an electroluminescent display.
In the display apparatus of the type applying a voltage between the opposite electrode and the electron-emitting devices to accelerate electrons emitted from the cold-cathode electron-emitting devices, a higher voltage is advantageously applied to maximize the brightness of the emitted light. Also, depending on the type of the electron-emitting devices, the emitted electron beam diverges until reaching the opposite electrode. From the viewpoint of realizing a display with higher resolution, therefore, it is advantageous that the distance between the electron source substrate and the opposite substrate is set to be small.
However, because the shorter distance between both the substrates necessarily generates a higher electric field in a space between both the substrates, the electron-emitting device can, in some occasions, become damaged due to an accidental discharge. In such a case, a current flows through the phosphor while the current concentrates in its part, thus causing a display screen to be partly brighter.
In order to solve the above-mentioned problems, it is required to reduce the probability of the accidental discharge or to make the discharge breakdown harder to occur.
Japanese Patent Laid-Open No. 2006-120622 (corresponding to EP 1638129A) and Japanese Patent Laid-Open No. 2006-173094 (corresponding to US 2006/0103294) disclose display apparatuses in which the discharge breakdown is made harder to occur. In the disclosed display apparatuses, a metal back is two-dimensionally divided into parts, which are interconnected through strip- or grid-shaped resistors, to thereby reduce a discharge current that flows in the event of an accidental discharge.
However, each of the image display apparatus disclosed in Japanese Patent Laid-Open No. 2006-120622 and No. 2006-173094 needs to be further improved not only in increasing the brightness, but also in realizing higher definition and higher quality of the displayed image.